1. Field of Invention
This invention relates to a junction box and more particularly relates to a junction box that is connected to a wire harness for an automobile vehicle and can easily change a circuit design. The present application claims priority to Japanese Application No. 2002-325472 filed on Nov. 8, 2002.
2. Description of Prior Art
Recently, as electrical components installed on an automobile vehicle have suddenly increased, circuits to be contained in a junction box have suddenly increased. In order to form branched circuits at a high density, the number of parts has extremely increased. This requires very many assembling steps.
The present applicant has proposed a junction box (Japanese Patent Public Disclosure 2001-359227), as shown in FIG. 7, in order to form a thin type junction box, to easily change a circuit design and to reduce assembling steps.
For convenience of explanation, a prior art junction box will be described by referring to FIGS. 7 and 8. FIG. 7 is an exploded perspective view of a conventional junction box. FIG. 8 is a perspective view of a part of a conventional connector module, illustrating problems in the module.
In a junction box 1, a connector connection circuit section (base circuit section), a fuse connection circuit section, and a relay connecting circuit section are divided into a connector module 2, a fuse module 3, and a relay module 4. These modules 2, 3, and 4 are assembled in a casing including an upper casing member 5 and a lower casing member 6.
In the connector module 2, bus bars 7 punched out into a desired circuit pattern from a sheet of a conductive metal plate are disposed on an insulation board 8 and a plurality of combinations of the bus bars 7 and insulation boards 8 are laminated on one another so that ends of the bus bars 7 project from peripheral edges of the insulation boards 8. In the fuse module 3 and relay module 4, bus bars 3b and 4b are secured to base plates 3a and 4a, respectively so that ends of the bus bars 3b and 4b project from peripheral edges of the base plates 3a and 4a. The ends of the bus bars 3b and 4b are connected to the ends of the bus bars 7 of the connector module 2 to form an electrical connection.
In the case where the junction box is divided into the connector module, fuse module, and relay module, the connector connection circuit, fuse connection circuit, and relay connecting circuit are also divided. Accordingly, only the corresponding module is changed, if a specification in the connector circuit, the fuse circuit, or the relay circuit is changed. Consequently, it is possible to easily comply with an alteration of specification.
Since the division of the circuits can eliminate overlap of tabs of the bus bars and avoid multiple layers of the bus bars, it is possible to reduce a thickness of the junction box. Furthermore, since an arrangement of the bus bars can be simplified, it is possible to reduce an area of the bus bars and suppress an increase of an area of the junction box.
However, in the case of changing circuits in the junction box 1, although only the corresponding modules 5, 6, and 8 are altered and a whole of the junction box 1 is not altered, at least one of the modules 5, 6, and 8 must be newly formed.
Furthermore, in the case of changing the circuits in accordance with a specification of an automobile vehicle mounting the junction box, it is necessary to prepare a certain kind of module every specification. This will increase the number of kinds of parts and the load of controlling the number of parts.
In order to overcome the above problems, as shown in FIG. 8, bus bars 7a-1 and 7a-2 in the connector module 2 are connected to each other by a bridging portion 7a-3 and the bridging portion 7a-3 may be either cut off or retained in accordance with the specification of an automobile vehicle to comply with an alteration of circuit design.
However, it is necessary to dispose the bus bars 7a1 and 7a-2 adjacent to each other in order to connect them by the bridging portion 7a-3. It is impossible to provide the bridging portion between a bus bar 7b and a bus bar 7c on different layers due to their structures. On the other hand, it is difficult to design the bus bars on a single layer to set the bridging portions. Even if such design is carried out, the number of stacked layers including the bus bars 7 and insulation boards 8 must be increased. This involves a problem of an increase in cost. Accordingly, there are limitations in the number of the patterns to provide changeable circuit patterns by selectively cutting off the bridging portions in the stacked circuits including the insulation boards 8 and bus bars 7a to 7b. 